[016/119] jffs2: Fix memory corruption in jffs2_read_inode_range()

Greg KH
2009-12-07T00:35:32Z

[-- Attachment #1: jffs2-fix-memory-corruption-in-jffs2_read_inode_range.patch --]
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2.6.31-stable review patch. If anyone has any objections, please let us know.

------------------
From: David Woodhouse <dwmw2@infradead.org>

commit 199bc9ff5ca5e4b3bcaff8927b2983c65f34c263 upstream.

In 2.6.23 kernel, commit a32ea1e1f925399e0d81ca3f7394a44a6dafa12c
("Fix read/truncate race") fixed a race in the generic code, and as a
side effect, now do_generic_file_read() can ask us to readpage() past
the i_size. This seems to be correctly handled by the block routines
(e.g. block_read_full_page() fills the page with zeroes in case if
somebody is trying to read past the last inode's block).

JFFS2 doesn't handle this; it assumes that it won't be asked to read
pages which don't exist -- and thus that there will be at least _one_
valid 'frag' on the page it's being asked to read. It will fill any
holes with the following memset:

memset(buf, 0, min(end, frag->ofs + frag->size) - offset);

When the 'closest smaller match' returned by jffs2_lookup_node_frag() is
actually on a previous page and ends before 'offset', that results in:

memset(buf, 0, <huge unsigned negative>);

Hopefully, in most cases the corruption is fatal, and quickly causing
random oopses, like this:

root@10.0.0.4:~/ltp-fs-20090531# ./testcases/kernel/fs/ftest/ftest01
Unable to handle kernel paging request for data at address 0x00000008
Faulting instruction address: 0xc01cd980
Oops: Kernel access of bad area, sig: 11 [#1]
[...]
NIP [c01cd980] rb_insert_color+0x38/0x184
LR [c0043978] enqueue_hrtimer+0x88/0xc4
Call Trace:
[c6c63b60] [c004f9a8] tick_sched_timer+0xa0/0xe4 (unreliable)
[c6c63b80] [c0043978] enqueue_hrtimer+0x88/0xc4
[c6c63b90] [c0043a48] __run_hrtimer+0x94/0xbc
[c6c63bb0] [c0044628] hrtimer_interrupt+0x140/0x2b8
[c6c63c10] [c000f8e8] timer_interrupt+0x13c/0x254
[c6c63c30] [c001352c] ret_from_except+0x0/0x14
--- Exception: 901 at memset+0x38/0x5c
LR = jffs2_read_inode_range+0x144/0x17c
[c6c63cf0] [00000000] (null) (unreliable)

This patch fixes the issue, plus fixes all LTP tests on NAND/UBI with
JFFS2 filesystem that were failing since 2.6.23 (seems like the bug
above also broke the truncation).

Reported-By: Anton Vorontsov <avorontsov@ru.mvista.com>
Tested-By: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/jffs2/read.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

--- a/fs/jffs2/read.c
+++ b/fs/jffs2/read.c
@@ -164,12 +164,15 @@ int jffs2_read_inode_range(struct jffs2_

/* XXX FIXME: Where a single physical node actually shows up in two
frags, we read it twice. Don't do that. */
- /* Now we're pointing at the first frag which overlaps our page */
+ /* Now we're pointing at the first frag which overlaps our page
+ * (or perhaps is before it, if we've been asked to read off the
+ * end of the file). */
while(offset < end) {
D2(printk(KERN_DEBUG "jffs2_read_inode_range: offset %d, end %d\n", offset, end));
- if (unlikely(!frag || frag->ofs > offset)) {
+ if (unlikely(!frag || frag->ofs > offset ||
+ frag->ofs + frag->size <= offset)) {
uint32_t holesize = end - offset;
- if (frag) {
+ if (frag && frag->ofs > offset) {
D1(printk(KERN_NOTICE "Eep. Hole in ino #%u fraglist. frag->ofs = 0x%08x, offset = 0x%08x\n", f->inocache->ino, frag->ofs, offset));
holesize = min(holesize, frag->ofs - offset);
}